He replied "guilty, your honour" nine times as magistrate Joe Chicchini read out charges dating back to September last year.

Voon operated his Successful Development and Therapy Centre in Cockburn in Perth's south until his arrest in Canada.It has been closed since and and he gave an undertaking to stop practising.

Voon attracted international media attention in May when he was arrested at a Canadian shopping mall.A video posted on news sites went viral showing Voon being confronted by an angry father demanding to see his phone and accusing him of filming his son's genitals in the public toilet at the Edmonton shopping centre.

Voon was granted bail in Canada but was arrested at Perth airport when he returned and the charges were bundled into the WA legal system.WA and federal police raided his Mount Pleasant home and business and seized electronic devices.

More charges were laid involving possession, obtaining or distributing child exploitation material involving hundreds of images and 12 videos, including more examples of him filming boys' genitals after following them into urinals in Australia, New Zealand and the US.

He is out on bail and will return to the District Court on January 27 ahead of sentencing.